Field of the Invention: This invention relates to the field of explosives, especially explosives having low sensitivity to impact. More particularly, the invention is directed to compositions loaded with high concentrations of 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazatetracyclo[5.5.0.05,903,11]dodecane, which is also known in the art and referred to herein as HNIW and, more commonly, CL-20. This invention is also directed to a process for making the explosive.
State of the Art: Nitramines are highly energetic compounds that have found acceptance in the art of explosives. Perhaps the most common nitramines in use in the explosives art today are 1,3,5-trinitro-1,3,5-triaza-cyclohexane (RDX) and 1,3,5,7-tetranitro-1,3,5,7-tetraaza-cyclooctane (HMX).
Another energetic nitramine that has found acceptance in the art is CL-20, which has a higher energetic performance than either RDX or HMX. The explosive composition LX-19, which is a combination of CL-20 and ESTANE (C5.14H7.5N0.187O1.76), is considered by many to be the current standard by which other explosives containing CL-20 are measured. Other examples of explosive compositions containing CL-20 as a primary energetic filler are disclosed in U.S. Pat. No. 6,214,137, entitled “High Performance Explosive Containing CL-20” and U.S. Pat. No. 6,217,799, entitled “Method for Making High Performance Explosive Formulations Containing CL-20.”
Although energetic performance is a crucial feature of energetic compositions, another important performance criteria by which explosive compositions are evaluated is shock sensitivity. An acceptably low shock sensitivity is extremely important to avoid accidental detonation, avoid hazardous conditions, and ensure the safe handling, shipment, and use of the material.
One test accepted in the art for measuring shock sensitivity is known as the Large Scale Gap Test (LSGT), in which a test material is placed into a metal tube on top of a witness plate. A predetermined number of PMMA (polymethylmethacrylate) cards are placed between the top of the metal tube and a booster material, which typically consists of 50 weight percent PETN (pentaerythritol tetranitrate) and 50 weight percent TNT (trinitrotoluene), available as Pentolite. The distance between the booster and the metal tube is expressed in cards, where one card is equal to 0.0254 cm (0.01 inch), such that 100 cards equal 2.54 cm (1 inch). A card gap measurement is the minimum number of cards required to prevent the booster from detonating the explosive sample, so that the sample does not blow a hole through the witness plate. Thus, the lower the card value, the lower the shock sensitivity of the explosive composition. The LSGT (or NOL Card Pipe Test) is more fully described in the Joint Technical Bulletin, Navy document number NAVSEA INST 8020.8B, Air Force technical order 11A-1-47, Defense Logistics Agency regulation DLAR 8220.1, and Army technical bulletin TB700-2.
LX-14, which is a combination of the more stable nitramine HMX and ESTANE, has an NOL card gap of 193 cards. The explosives disclosed in U.S. Pat. No. 6,214,137 and U.S. Pat. No. 6,217,799 exhibited similar shock sensitivities to LX-14.